M——. "We should avoid what gives us pain."

S——. "Yes, to be sure."

M——. "Whatever burns us, gives us pain."

S——. "Yes, that it does!"

M——. "We should then avoid whatever burns us."

To this conclusion S—— heartily assented, for he had but just recovered from the pain of a burn.

M——. "Fire burns us."

S——. "Yes, I know that."

M——. "We should then avoid fire."